1. Field of the Invention
The present invention generally relates to manually powered fastening devices, and more specifically to impact driven staple guns and tacking machines.
2. Description of the Related Art
The fastening tool of the present invention is similar to that disclosed in co-pending application Ser. No. 07/899,748, filed Jun. 17, 1992, and U.S. Pat. No. 5,165,587, issued Nov. 24, 1992 to Joel Marks. The fastening tool enables an operator's single hand to compress a spring to store and instantly release the energy of the spring to expel a staple from the fastening tool by an impact blow. The fastening tool incorporates a forward acting actuator lever. The staples exit towards the front end of the fastening tool while the lever is hinged near the rear end of the fastening tool. The tool may be gripped through an opening in the body of the tool. The opening extends to the front of the tool, and in certain configurations, the opening may originate at the front of the body of the tool.
U.S. Pat. No. 2,671,215 issued to Abrams discloses the familiar Arrow stapler. A lever is pivoted towards the front of the staple gun. Pressing down the lever behind the pivot compresses a coil spring and raises a plunger through a pivotally attached actuating arm. At a pre-determined point of the lever travel, the actuating arm has arced rearward sufficiently such that it releases the plunger assembly. The plunger is driven downwards by the force stored in the coil spring. The coil spring is located immediately adjacent to, or above, the plunger. The plunger is located in the front of the staple gun.
U.S. Pat. No. 3,610,505 issued to Males discloses a design similar to the Abrams design. A lever is pivoted near the front of a staple gun. Pressing the extended arm of the lever downwards towards the rear of the staple gun causes a coil spring to compress and simultaneously raises a plunger. Once the lever has been lowered past a predetermined point, the lever is released from the coil spring and plunger assembly by the force of a cam assembly, and the force stored in the coil spring is allowed to drive the plunger downwards, striking and ejecting a staple. The plunger is located at the front of the staple gun.
U.S. Pat. No. 2,326,540 issued to Krantz discloses a staple gun in which the actuation lever is pivoted towards the rear of the staple gun. Through a series of levers, this action is connected to a coil spring and plunger located at the front of the staple gun. As the lever arm is lowered, the spring is compressed and the plunger is raised. A pivotable member of the spring and plunger assembly links the levers to the assembly. Once the lever reaches a predetermined point, the pivotable member is forcibly disengaged from the lifting lever, and the energy stored in the coil spring is allowed to release, driving the plunger downward, striking and expelling a staple.
U.S. Pat. No. 2,769,174 issued to Libert describes a staple gun in which the actuation lever is pivoted at a point towards the rear of the staple gun, and staples are expelled out of the front of the staple gun. Pressing down on the actuation arm towards the bottom of the staple gun actuates a series of levers and compresses a coil spring to raise the plunger. At a predetermined point, two of the levers are forcibly decoupled and the energy stored by the coil spring is allowed to release, driving the plunger downwards, striking and expelling a staple.
U.S. Pat. No. 4,629,108 issued to Judge describes a staple gun contained within a stamped metallic frame which is enclosed in a second stamped or molded housing. Judge describes a common mechanism to accommodate an actuation lever pivoted near the rear of the staple gun. The release mechanism appears to be similar to that of Libert.
U.S. Pat. No. 3,862,712 issued to LaPointe et al. discloses a staple guiding track which slides rearward to expose a chamber in the staple gun body into which staples are placed. The staple gun is inverted during this operation. This sliding mechanism requires numerous components and assembly operations for its manufacture.
U.S. Pat. No. 4,452,388 issued to Fealy comprises a staple gun with an intermediately actuated leaf spring. The multi-layered leaf spring spans the length of the tool body. A mechanism pulls upward upon the spring to lift the spring and plunger. The mechanism is then forced away from the spring to release the spring from the actuating mechanism.
Typical of the prior art, the above described designs use either of two release methods. By one method a cam or stop acts upon a linking member to force a de-linkage at the release position. By the other method a rotating actuating member is slidably linked to a reciprocating plunger member. At the release position the actuating member has rotated out of the plane of motion of the plunger member, and the plunger member is released.
The above release methods may be called active or direct releases because the release is forcibly and directly caused by the actuating members. The first method requires a substantial increase in operating force to enable the forced release action. The second method provides only a vague release action since there is no secondary event to cause the release. No distinct action occurs at the release position.